1. What is Odds Ratio?

The odds ratio (OR) is a measure of association between an exposure and an outcome. It represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.

2. How Does the Calculator Work?

The calculator uses the odds ratio formula:

Where:

• \( a \) — Exposed with outcome
• \( b \) — Exposed without outcome
• \( c \) — Unexposed with outcome
• \( d \) — Unexposed without outcome

Explanation: The odds ratio compares the odds of the outcome in the exposed group versus the unexposed group.

3. Interpretation of Results

Details:

• OR = 1: No association
• OR > 1: Positive association (higher odds with exposure)
• OR < 1: Negative association (lower odds with exposure)

The p-value indicates statistical significance (typically p < 0.05 is considered significant).

4. Using the Calculator

Tips: Enter the counts for each cell in the 2×2 contingency table. All values must be non-negative integers.

5. Frequently Asked Questions (FAQ)

Q1: When should I use odds ratio vs relative risk?
A: Odds ratio is preferred in case-control studies, while relative risk is used in cohort studies.

Q2: What does an OR of 2.5 mean?
A: The odds of the outcome are 2.5 times higher in the exposed group compared to the unexposed group.

Q3: How is the p-value calculated?
A: The p-value is typically calculated using Fisher's exact test or chi-square test, depending on sample size.

Q4: What if one of my cells has a zero?
A: The calculator can handle zeros, but interpretation becomes more difficult. Consider adding 0.5 to all cells (Haldane correction).

Q5: What are confidence intervals for odds ratio?
A: Confidence intervals (not shown here) provide the range of likely values for the true odds ratio in the population.